diff --git a/src/rsprocess/element.rs b/src/rsprocess/element.rs
new file mode 100644
index 0000000..45b0a06
--- /dev/null
+++ b/src/rsprocess/element.rs
@@ -0,0 +1,52 @@
+use serde::{Serialize, Deserialize};
+use std::fmt;
+
+use super::translator::PrintableWithTranslator;
+
+pub type IdType = u32;
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
+pub enum IdState {
+    Positive,
+    Negative
+}
+
+impl fmt::Display for IdState {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+	match self {
+	    Self::Positive => write!(f, "+"),
+	    Self::Negative => write!(f, "-")
+	}
+    }
+}
+
+impl std::ops::Not for IdState {
+    type Output = Self;
+
+    fn not(self) -> Self::Output {
+	match self {
+	    Self::Positive => Self::Negative,
+	    Self::Negative => Self::Positive
+	}
+    }
+}
+
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
+pub struct PositiveType {
+    pub id: IdType,
+    pub state: IdState
+}
+
+impl PrintableWithTranslator for PositiveType {
+    fn print(&self,
+	     f: &mut fmt::Formatter,
+	     translator: &super::translator::Translator)
+	     -> std::fmt::Result {
+	write!(f,
+	       "{}{}",
+	       self.state,
+	       translator.decode(self.id).unwrap_or("Missing".into())
+	)
+    }
+}
diff --git a/src/rsprocess/set_test.rs b/src/rsprocess/set_test.rs
new file mode 100644
index 0000000..2af1918
--- /dev/null
+++ b/src/rsprocess/set_test.rs
@@ -0,0 +1,78 @@
+#[test]
+fn prohibiting_set_1() {
+    use std::collections::BTreeMap;
+
+    use super::set::{Set, PositiveSet};
+    use super::element::IdState;
+
+    let r1r = Set::from(vec![2, 3, 4]);
+    let r1i = Set::from(vec![5, 6, 7]);
+
+    let r2r = Set::from(vec![2, 3, 11]);
+    let r2i = Set::from(vec![5, 6, 7]);
+
+    let prohibiting_set = Set::prohibiting_set(&[r1r, r2r], &[r1i, r2i]).unwrap();
+
+    assert_eq!(prohibiting_set,
+	       vec![PositiveSet { identifiers:
+				  BTreeMap::from([(2, IdState::Negative)]) },
+		    PositiveSet { identifiers:
+				  BTreeMap::from([(3, IdState::Negative)]) },
+		    PositiveSet { identifiers:
+				  BTreeMap::from([(5, IdState::Positive)]) },
+		    PositiveSet { identifiers:
+				  BTreeMap::from([(6, IdState::Positive)]) },
+		    PositiveSet { identifiers:
+				  BTreeMap::from([(7, IdState::Positive)]) },
+		    PositiveSet { identifiers:
+				  BTreeMap::from([(4, IdState::Negative),
+						  (11, IdState::Negative)]) }])
+}
+
+#[test]
+fn prohibiting_set_2() {
+    use std::collections::BTreeMap;
+
+    use super::set::{Set, PositiveSet};
+    use super::element::IdState;
+
+    let r1r = Set::from(vec![1]);
+    let r1i = Set::from(vec![2]);
+
+    let r2r = Set::from(vec![1]);
+    let r2i = Set::from(vec![3]);
+
+    let prohibiting_set = Set::prohibiting_set(&[r1r, r2r], &[r1i, r2i]).unwrap();
+
+    assert_eq!(prohibiting_set,
+	       vec![PositiveSet { identifiers:
+				  BTreeMap::from([(1, IdState::Negative)]) },
+		    PositiveSet { identifiers:
+				  BTreeMap::from([(2, IdState::Positive),
+						  (3, IdState::Positive)]) }])
+}
+
+
+#[test]
+fn prohibiting_set_3() {
+    use std::collections::BTreeMap;
+
+    use super::set::{Set, PositiveSet};
+    use super::element::IdState;
+
+    let r1r = Set::from(vec![1]);
+    let r1i = Set::from(vec![2]);
+
+    let r2r = Set::from(vec![3]);
+    let r2i = Set::from(vec![1]);
+
+    let prohibiting_set = Set::prohibiting_set(&[r1r, r2r], &[r1i, r2i]).unwrap();
+
+    assert_eq!(prohibiting_set,
+	       vec![PositiveSet { identifiers:
+				  BTreeMap::from([(1, IdState::Negative),
+						  (3, IdState::Negative)]) },
+		    PositiveSet { identifiers:
+				  BTreeMap::from([(2, IdState::Positive),
+						  (3, IdState::Negative)]) }])
+}